Collision energy absorbing structure of vehicle

ABSTRACT

Disclosed is a collision energy absorbing structure of a vehicle capable of relieving impact by using a tubular pipe member having equally-sized rectangular cross section and equal plate thickness and including no inside ribs and by adding a suitable trigger, and being easily manufactured at a low cost. By forming a cutout portion on the left side of the front end portion of the collision energy absorbing structure, the deformation starting portion is provided. The cutout portion is formed at parts of three flat plate portions comprised of one of the four flat plate portions and corresponding opposite portions thereof. The general portion, which follows the deformation starting portion, is tubular with rectangular cross section and has a closed cross-section structure.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional patent application of U.S.patent application Ser. No. 10/116,604 filed on Apr. 4, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a collision energy absorbing structureof a vehicle which is used for absorbing a collision energy generated bya collision of vehicles such as railroad vehicles by bellows-likedeformation (plastic deformation) of a tubular energy absorbing memberwith rectangular cross section to relieve impact when collision occurs.

2. Description of the Related Art

In general, it is known that a pipe member can be used as an energyabsorbing member for absorbing a collision energy by bellows-likedeformation, because the pipe member is plastically deformed likebellows while suppressing deformation of the Euler buckling when acompression force is axially applied to the pipe member by suitablyselecting a dimension or a thickness thereof. Since such bellows-likedeformation is capable of stably absorbing the collision energy,conventionally, the collision energy absorbing structure using the pipemember has been widely used.

By the way, since a high reaction force is generated in triggering thebellows-like deformation when such pipe member is used to form thecollision energy absorbing structure, the impact acting on passengers isincreased in an initial stage of collision. Accordingly, the followingstructure has been proposed as a structure for reducing the maximumforce in the initial stage of collision.

-   (1) By way of example, in a structure disclosed in Japanese Patent    No. 2650527 in which ribs are longitudinally formed integrally with    the inside of a member body extruded to have closed cross section    and provided in the longitudinal direction of the vehicle to define    a plurality of parts in the member body, the ribs have inclined    portions at end portions thereof which are extending from points    connecting the ribs to peripheral portions of the member body toward    the inside of the body. In this structure, since the inclined    portions are thus formed in the ribs at end face portion of the    member body and the corresponding rib cross-sectional areas are    extremely small, the member body tends to be axially deformed by    buckling upon application of an axial collision force to the end    portion of the member body in collision of the vehicle.    Consequently, an initial reaction force can be reduced.-   (2) As another example, as disclosed in Japanese Patent No. 2882243,    a plurality of arc-shaped grooves inwardly recessed and axially    extending from the front end are formed circumferentially and at    substantially equal intervals at the front end portion of a tubular    chassis frame provided in the longitudinal direction of the vehicle.    In this structure, upon application of impact to the front end    portion from front, the arc-shaped groove portions and the portions    without the grooves are continuously and axially deformed by    buckling while being deformed alternately and inwardly or outwardly    from the front end, so that plastic deformation is stabilized with    bellows being close to one other.-   (3) As a further example, as disclosed in Publication of Examined    Patent Application No. Hei. 11-5564, a side member of a vehicle    formed to have a hollow shaft by extruding aluminum is provided with    at least one rib in the longitudinal direction thereof and the    thickness of the rib and the thickness of the side member are    gradually increased from the end portion toward a vehicle chamber    side in the longitudinal direction of the vehicle. Because of such a    gradual increase in the thickness, this structure is capable of    reducing an initial maximum force while keeping a collision energy    absorbing ability large as the whole.-   (4) As a still further example, as disclosed in Publications of    Examined Patent Applications Nos. Hei. 9-277953, 9-277954, in an    energy absorbing member capable of absorbing a collision energy by    bellows-like bucking deformation, a cross section of a buckling    deformation starting end is a polygon-shaped closed cross section    with angles more than 4 and a cross section of the other end is a    polygon-shaped closed cross section having sides more than those of    the cross section of the starting end, between which the cross    section gradually varies. These structures enable the increasing of    the buckling force and the reducing of the initial impact force by    utilizing the polygon-shaped cross section or a tapered shape with    varying cross section to suppress the initial impact force or    stabilize the first buckling deformation.

However, the structures of (1)-(4) suffer from the following drawbacks.

-   (A) In the structure disclosed in Japanese Patent No. 2650527, since    the inclined portions are formed at the ribs inside of the member    body, its structure is complicated. In addition, this structure is    only applicable to the structure having inside ribs (e.g., extruded    aluminum).-   (B) The structure disclosed in Japanese Patent No. 2882243 is    applicable only to the cylindrical frame. Since the bellows-like    deformation tends to be unstable in the cylindrical frame as    compared to the tubular frame with rectangular cross section, a    stable energy absorbing characteristic is difficult to obtain.-   (C) In the structures disclosed in Publications of Examined Patent    Applications Nos. Hei. 11-5564, 9-277953, 9-277954, since the pipe    member (side member or energy absorbing member) has a structure with    the cross section varying in the axial direction thereof, a special    and complicated process is needed.

SUMMARY OF THE INVENTION

The present invention addresses the above-described condition, and anobject of the present invention is to provide a collision energyabsorbing structure of a vehicle capable of absorbing impact by using atubular pipe member having an equally-sized rectangular cross sectionand an equal plate thickness and including no inside ribs and by addinga suitable trigger, and being easily manufactured at a low cost.

To achieve the above object, according to the present invention, thereis provided a collision energy absorbing structure of a vehiclecomprising: a tubular energy absorbing member with rectangular crosssection, provided in the longitudinal direction of the vehicle andhaving four flat plate portions, the tubular energy absorbing memberbeing adapted to receive a collision force in the longitudinal directionof the vehicle and deformed like bellows by buckling, so as to absorb acollision energy; and a deformation starting portion provided by forminga cutout portion in one of right and left sides or one of upper andlower sides of a front end portion of the energy absorbing member.

According to the present invention, the strength of the deformationstaring portion is lower than the strength of the other part of theenergy absorbing member and the initial impact force can be reduced. Inaddition, since the deformation starting portion is provided by reducingthe size of part of the tubular energy absorbing member with rectangularcross section, the structure can be simplified.

In the collision energy absorbing structure, the deformation startingportion may be provided by forming a cutout portion in one end of rightand left sides or one of upper and lower sides of a front end portion ofthe energy absorbing member. Also, the cutout portion may be formed inparts of three flat plate portions comprised of one of the four flatplate portions and flat plate portions located on both sides thereof. Byincreasing/reducing the number of the energy absorbing members, theamount of absorbed energy can be adjusted in the whole structure. Thetubular member needs to have four flat plate portions and may havesquare or rectangular cross section. The energy absorbing member may bemanufactured by forming the cutout portion at the front end portion ofthe tubular member with rectangular cross section (closed cross sectionstructure), or otherwise, by opposing open sides of two channel membershaving different lengths because of the cutout portion to each other andbonding flanges thereof together.

The tubular energy absorbing member may have a portion extended frompart of the front end portion so as to be substantially channel shaped.The provision of the cutout portion at the front end portion of theenergy absorbing member is equivalent to the provision of the extendedportion at the front end portion.

In this constitution, upon application of the force in the longitudinaldirection of the vehicle when collision occurs, since the front endportion is provided with the cutout portion and has the open crosssection, i.e., provided with the extended portion, the initial forcepeak for generating the bellows-like deformation can be reduced ascompared to the case where the tubular portion (closed cross sectionstructure) is deformed like bellows without the cutout portion.

Since the front end portion (extended portion) has already started to bedeformed, the following tubular portion starts to be deformed likebellows naturally. More specifically, the deformation sequentiallyoccurs in the front end portion (extended portion) and the portioncontinuous with the front end portion, while the portion provided withthe cutout portion starts to be newly deformed like bellows after thebellows-like deformation of the front end portion, so that the forcepeak for generating the new bellows-like deformation is reduced and thebellows-like deformation naturally takes place. Consequently, thecollision energy can be efficiently absorbed.

Further, since the tubular pipe with rectangular cross section isprovided with the cutout portion, that is, the channel-shaped extendedportion, the energy absorbing member can be manufactured easily and at alow cost. In particular, since the front end portion is provided withthe cutout portion, i.e., the extended portion so as to be vertically orlaterally asymmetric, the reaction force in the initial stage ofcollision can be reduced with such simple structure. Also, since thebellows-like deformation has already started in part (asymmetricportion) of the front end portion, the reaction force at the start ofdeformation of the other portion is reduced to be substantially equal tothe reaction force in the initial stage of the collision (see FIG. 2),thereby keeping a constant reaction force. Consequently, the impactacting on the passengers can be relieved without a rapid rise in theimpact force.

Also, a plurality of impact absorbing members may be provided so as tobe vertically or laterally symmetric.

In this constitution, since the plurality of energy absorbing membersare vertically or laterally symmetric, the impact in the travelingdirection is evenly applied to the front end portions (extendedportions) of these energy absorbing members, so that the bellows-likedeformation occurs naturally without falling the energy absorbingmembers.

The collision energy absorbing structure may further comprise: a rubberdamper connected to a coupler of the vehicle, for absorbing andrelieving impact generated between vehicles, and a front end portion ofthe energy absorbing member may be connected to a rear end portion ofthe rubber damper and a rear end portion of the energy absorbing membermay be connected to a draft stop mounted to a vehicle body frame.

With this constitution, the small collision energy can be absorbed bythe rubber damper and the great collision energy can be absorbed bybellows-like deformation of the energy absorbing member.

In the collision energy absorbing structure, the energy absorbing membermay be provided behind a rail guard board for eliminating obstacles on arail during traveling and a rear end portion of the energy absorbingmember may be connected to a support device mounted to a vehicle bodyframe.

With this constitution, when the excessive collision energy is appliedto the rail guard board for eliminating obstacles on the rail duringtraveling, this collision energy is absorbed by the bellows-likedeformation of the energy absorbing member.

The collision energy absorbing structure, may further comprise: asupport device mounted to a vehicle body frame, provided behind acoupler and extending forwardly of a rail guard board, and in thisstructure, a rear end portion of the energy absorbing member may beconnected to a front end portion of the support device, and the energyabsorbing member may extend forwardly of the coupler.

In this constitution, since the energy absorbing member extendingforwardly of the coupler in the front vehicle is provided with thecollision member at the front end thereof, the collision member iscollided and the collision energy is absorbed by the bellows-likedeformation of the energy absorbing members. Consequently, the impactacting on the passengers can be relieved.

The above and further objects and features of the invention will morefully be apparent from the following detailed description withaccompanying drawings.

BRIEF DESCRIPTION OF THE BRIEF DRAWINGS

FIG. 1 is a perspective view showing a front end portion of an energyabsorbing member used in a collision energy absorbing structure of avehicle according to the present invention;

FIG. 2 is a view showing a result of a computer simulation analysis ofthe relationship between displacement and force applied to the energyabsorbing member according to the present invention;

FIG. 3 is an explanatory view schematically showing a first stage of adeformation mode of the front end portion of the energy absorbing memberaccording to the present invention;

FIG. 4 is an explanatory view schematically showing a second stage ofthe deformation mode of the front end portion of the energy absorbingmember according to the present invention;

FIG. 5 is an explanatory view schematically showing a third stage of thedeformation mode of the front end portion of the energy absorbing memberaccording to the present invention;

FIG. 6 is an explanatory view schematically showing a fourth stage ofthe deformation mode of the front end portion of the energy absorbingmember according to the present invention;

FIG. 7 is an explanatory view schematically showing a fifth stage of thedeformation mode of the front end portion of the energy absorbing memberaccording to the present invention;

FIG. 8 is an explanatory view schematically showing a sixth stage of thedeformation mode of the front end portion of the energy absorbing memberaccording to the present invention;

FIG. 9 is an explanatory view schematically showing a seventh stage ofthe deformation mode of the front end portion of the energy absorbingmember according to the present invention;

FIG. 10 is an explanatory view schematically showing an eighth stage ofthe deformation mode of the front end portion of the energy absorbingmember according to the present invention;

FIG. 11 is an explanatory view schematically showing a ninth stage ofthe deformation mode of the front end portion of the energy absorbingmember according to the present invention;

FIG. 12(A) is a graph showing the relationship between a first peakforce generated in an initial stage of collision and a size of adeformation starting portion;

FIG. 12(B) is a graph showing the relationship between a second peakforce generated in a middle stage of collision and a size of thedeformation staring portion;

FIG. 12(C) is a graph showing the relationship between a ratio betweenthe first peak force and the second peak force and a size of thedeformation starting portion;

FIG. 13 is a side view showing an example in which a collision energyabsorbing structure of a vehicle according to the present invention isapplied to a coupler of a railroad vehicle;

FIG. 14 is a plan view showing the collision energy absorbing structureof the vehicle of FIG. 13;

FIG. 15 is a side view showing an example in which the collision energyabsorbing structure of the vehicle according to the present invention isapplied to a rail guard of a front vehicle of the railroad vehicle;

FIG. 16 is a plan view showing a collision energy absorbing structure ofthe vehicle of FIG. 15;

FIG. 17 is a side view showing an example in which the collision energyabsorbing structure of the vehicle according to the present invention ismounted to a front portion of a front vehicle of the railroad vehicle;and

FIG. 18 is a plan view showing the collision energy absorbing structureof the vehicle of FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment of the present invention will bedescribed with reference to drawings.

FIG. 1 is a perspective view showing an energy absorbing member used ina collision energy absorbing structure of a vehicle according to thepresent invention.

Referring now to FIG. 1, there is shown a tubular energy absorbing pipemember 1 (energy absorbing member) with rectangular cross section. Theenergy absorbing pipe member 1 is provided with a cutout portion 1 ahaving an axial dimension L and a width dimension B on the left side ofa front end portion S1 which corresponds to a deformation startingportion that has channel-shaped open cross section and is laterallyasymmetrical. Here, the width dimension B of the cutout portion 1 a isequal to substantially ½ of a width W of the member 1.

The energy absorbing pipe member 1 has a closed cross-section structurehaving four flat plate portions 1A, 1B, 1C, 1D and the cutout portion 1a is formed by the flat plate portion 1A and parts of the flat plateportions 1B, 1C connected to both sides of the flat plate portion 1A atthe front end portion (deformation starting portion) S1. The front endportion S1 provided with the cutout portion 1 a functions as a triggerportion for triggering bellows-like deformation for energy absorptionand has the channel-shaped open cross section. While corner portions ofthe cutout portion 1 a have certain degrees, for example, 90 degrees inFIG. 1, they may be curved.

In other words, the channel-shaped deformation starting portion(extended portion) S1 is extended from the whole width of the flat plateportion 1A, and part of the flat plate portion 1B and part of the flatplate portion 1C. The extended portion S1 has a length L as shown inFIG. 1.

When the axial force is evenly applied to the front end face of thetubular energy absorbing pipe member 1 with rectangular cross section,deformation (bellows-like deformation) that is laterally asymmetricstarts from the deformation starting portion S1 corresponding to theextended portion having low strength. In brief, the deformation startingportion S1 is deformed in the initial stage of collision, whichdeformation triggers the bellows-like deformation mentioned later.

In the bellows-like deformation (buckling deformation) of thedeformation starting portion S1 (trigger portion) in the initial stageof collision, since the deformation starting portion S1 is laterallyasymmetrical and has the open cross section because of the cutoutportion 1 a and initial force necessary for generating the bellows-likedeformation as the result of collision is therefore small, the peak ofthe initial force in the collision is considerably reduced as comparedto the case where the tubular pipe member 1 with rectangular crosssection is deformed like bellows without the cutout portion 1 a.

Then, the bellows-like deformation (buckling deformation) of thedeformation starting portion S1 (right-half portion) of the energyabsorbing pipe member 1 gradually progresses and reaches a generalportion S2 as the closed cross section. Since the asymmetricbellows-like deformation has been already generated, new bellows-likedeformation does not occur in the entire general portion S2, but occursin the left half portion of the general portion S2. So, there is adifference between the time when the initial force (force peak) at thestart of the buckling deformation of the deformation starting portion S1is generated and the time when the initial force at the start of thebuckling deformation of the general portion S2 is generated. For thisreason, the force necessary for causing the bellows-like deformation inthe energy absorbing pipe member 1 is divided into the force at thestart of the bellows-like deformation of the deformation startingportion S1 and the force for the start of the bellows-like deformationof the general portion S2. As a result, the peak force in the initialstage of collision is reduced and a constant reaction force is kept.Therefore, the impact acting on the passengers is relieved without arapid rise in the impact force.

Thus, the bellows-like deformation of the deformation starting portionS1 triggers the bellows-like deformation of the general portion S2. Oncethe bellows-like deformation occurs in the general portion S2, stablebellows-like deformation continues thereafter. In this case, since theaxial (longitudinal) force applied to the energy absorbing pipe member 1is considerably higher than the force orthogonal to the axial force,transitions of the bellows-like deformation from the deformationstarting portion S1 to the general portion S2 smoothly takes place.

FIG. 2 shows a result of computer simulation analysis of therelationship between the force and displacement of this deformation.FIGS. 3 through 11 are views schematically showing change occurring whenthe collision force is applied to a contact plate 2 provided at thefront end of the energy absorbing pipe member 1. In the state of FIG. 3before collision, no force is applied and the forces in the states ofFIGS. 4 through 11 correspond to the forces at force peak points P1-P8in FIG. 2. As shown in FIGS. 3 through 11, the contact plate 2 isprovided on the deformation starting portion S1 of the energy absorbingpipe member 1. In these cases, the cutout portion 1 a is formed at theupper half portion of the front end portion (see FIGS. 4 through 11). Inother words, the deformation starting portion (extended portion) S1 isextended from the lower half portion of the front end of the energyabsorbing pipe member 1.

The state before collision is shown in FIG. 3. Once the collision occursand the axial collision force (dynamic force) is applied through thecontact plate 2, first, the deformation starting portion S1corresponding to the lower half portion of the energy absorbing pipemember 1 starts to be deformed by buckling. Then, as shown in FIG. 5,the upper flat plate portion of the upper half portion of the closedcross-section structure of the energy absorbing pipe member 1 starts tobe deformed by buckling, and then, as shown in FIG. 6, right and leftflat plate portions of the closed cross-section structure starts to bedeformed by buckling. In this case, a force peak point P1 correspondingto FIG. 4 at which the deformation starting portion S1 startsbellows-like deformation is substantially equal to a force peak point P2corresponding to FIG. 5 at which the general portion S2 startsbellows-like deformation, although the force peak point P2 is slightlygreater than the force peak point P1, thus keeping a constant reactionforce.

Once the bellows-like deformation starts, the buckling deformation ofthe upper and lower flat plate portions (see FIGS. 7, 9, and 11) and thebuckling deformation of the right and left flat plate portions (seeFIGS. 8, 10) are alternately repeated. Also, in these cases, theconstant reaction force can be maintained without significant forcefluctuation.

The reason why the reaction force in the initial stage of the collisiondecreases as shown in FIG. 2, is that there is a difference between thetime when the buckling deformation of the upper flat plate portionstarts and the time when the buckling deformation of the lower flatplate portion starts in the states of FIGS. 4, 5, and in the state ofFIG. 6 and thereafter, the deformation in its previous stage facilitatesthe buckling deformation.

Also, the deformation in the initial stage is asymmetric (see FIGS. 4through 6) and then becomes symmetric. This is because the bucklingdeformation of the right and left flat plate portions starts fromdeformation oblique with respect to the axial direction in the state ofFIG. 7, and with a progress, this deformation gradually changes intodeformation in the direction orthogonal to the axial direction.

Subsequently, simulation analysis results of how the size of the cutoutportion 1 a affects the initial force will be explained with referenceto FIGS. 12(A), (B), (C). In FIGS. 12(A), 12(B), 12(C), B denotes awidth of the cutout portion 1 a, L denotes an axial length of the cutoutportion 1 a, and Ac, As respectively denote the cross-sectional area ofthe deformation starting portion S1 and the cross-sectional area of thegeneral portion S2.

As can be seen from FIG. 12(A), the first peak force generated justafter the collision tends to decrease with an increase in the size ofthe cutout portion 1 a i.e., with an increase in Ac/As, whereas, as canbe seen from FIG. 12(B), the following second peak force tends toincrease with the increase in the cutout portion 1 a.

Since it is desirable that there is no great difference between thefirst and second peak forces and the force fluctuates evenly, judgingfrom FIG. 12(C), the ratio Ac/As between the cross-sectional area of thedeformation starting portion S1 and the cross-sectional area of thegeneral portion S2 is preferably approximately 0.5. It is confirmed thatthe similar tendency and results are obtained in the tubular member withsquare cross section and the tubular member with rectangular crosssection.

EXAMPLE 1

In this example, the energy absorbing member is applied to a coupler ofa railroad vehicle.

Referring to FIGS. 13, 14, a rubber damper 11 comprises a draft stop 12having a front support portion 12 a and a rear support portion 12 b,front and rear impact absorbing rubbers 13 a, 13 b respectively providedin the front support portion 12 a and the rear support portion 12 b ofthe draft stop 12, a pair of connecting rod members 14R, 14L forrespectively connecting and fixing the impact absorbing rubbers 13 a, 13b (rubber plates) to the draft stop 12, and flange members 15 a, 15 brespectively mounted to a front portion of the connecting rod member 14Rand a rear portion of the connecting rod member 14L and interposing theimpact absorbing rubbers 13 a, 13 b in the draft stop 12. The front endportions of the connecting rod members 14L, 14R are connected to a frontsupport frame 16F, which is connected to a rear end portion of a coupler18 with an intermediate member 17 interposed therebetween.

Front end portions of a pair of energy absorbing pipe members 19L, 19Rare connected to the rear flange member 15 b and rear end portions ofthe energy absorbing pipe members 19L, 19R are connected to a rearsupport frame 21 supported by a vehicle body frame 20. The energyabsorbing pipe members 19L, 19R are laterally symmetric such that cutoutportions 19 a, 19 b are inwardly opposed for enabling the well-balancedreception of impact force. In other words, the energy absorbing pipemembers 19L, 19R are placed to allow the deformation starting portions19 c, 19 d respectively provided at front ends of the energy absorbingpipe members 19L, 19R to be located outerly.

With this constitution, by supporting the rubber damper 11 by means ofthe energy absorbing pipe members 19L, 19R (energy absorbing members),the collision energy remaining partially unabsorbed as the result ofdeformation by the rubber damper 11 is absorbed by the bellows-likedeformation (plastic deformation) of the energy absorbing pipe members19L, 19R. In a case where a railroad vehicle comprised of a plurality ofvehicles collides with another vehicle, the energy absorbing ability ofthe energy absorbing pipe members 19L, 19R complements the energyabsorbing ability of the rubber damper 11 when insufficient, and theevent that the vehicle is severely damaged or significant impact acts onpassengers can be avoided.

EXAMPLE 2

In this example, the energy absorbing member is applied to a rail guardof a front vehicle of a railroad vehicle.

Referring to FIGS. 15, 16, a rail guard board 31 for eliminatingobstacles is bent like horseshoe and mounted and fixed to a vehicle bodyframe 32. Two energy absorbing pipe members 33 are placed behind therail guard board 31 so as to be spaced apart therefrom. These energyabsorbing pipe members 33 are coupled by means of a coupling member 33 band supported by a support device 34. More specifically, the flat-plateshaped coupling member 33 b is connected to tip ends of the respectiveenergy absorbing pipe members 33 and rear ends of the members 33 arefixed to the support device 34. An upper end portion of the supportdevice 34 is fixed to the vehicle body frame 32. In this case, thecutout portions 33 a of the respective energy absorbing pipe members 33are opened outwardly (or inwardly) and laterally symmetric as shown inFIG. 16. In other words, the energy absorbing pipe members 33 arelaterally symmetric to allow deformation staring portions 33 c providedat front ends of the energy absorbing pipe members 33 to be inwardlylocated. Reference numeral 50 denotes a rail.

With this constitution, the energy, which remains partially unabsorbedas the result of the deformation of the rail guard board 31, is absorbedby the energy absorbing pipe members 33, thereby relieving the impact onthe vehicle body frame 32.

In addition, lightweight is achieved. Specifically, although the energyremaining partially unabsorbed as the result of the deformation of therail guard board has been conventionally absorbed by the energyabsorbing plate composed of flat springs and provided behind the frontside of the rail guard board, and the weight is correspondinglyincreased, the use of the energy absorbing pipe members 33 providessignificant lightweight.

EXAMPLE 3

In this example, the impact absorbing member is mounted to the frontportion of the front vehicle of the railroad vehicle to absorb thecollision energy when front vehicles head-on collide.

Referring to FIGS. 17, 18, an energy absorbing pipe member 43 isprovided between a coupler 41 located on an upper side and a rail guardplate 42 located on a lower side in the vertical direction. A supportpipe member 45 is provided so as to extend in the longitudinal directionof the vehicle from a support device 44 and a rear end portion of theenergy absorbing pipe member 43 provided with a tip member 46 isconnected to a tip end portion of the support pipe member 45.

The support pipe member 45 extends forwardly of the rail guard board 42and has a length so as to be located behind the coupler 41. When thevehicle is not used as the front vehicle, the energy absorbing pipemember 43 is removed from the vehicle to allow vehicles to beinterconnected by means of the coupler 41. Reference numeral 48 denotesa vehicle body frame. At a portion where the energy absorbing pipemember 43 is connected to the tip member 46, the cutout portion 43 a isprovided at a lower portion thereof and laterally symmetric. In otherwords, the energy absorbing pipe member 43 is placed so that adeformation starting portion 43 b extended from the tip end of theenergy absorbing pipe member 43 is located on the upper side. The tipmember 46 is located in a cover 47 on the tip side. Similarly to theexamples, 1, 2, it is needless to say that two energy absorbing pipemembers symmetrically placed may support a collision member.

With this constitution, when the front vehicles collide with each other,the tip member 46 collides with the tip member 46 of the opposedvehicle, thereby causing the energy absorbing pipe member 43 to bedeformed by buckling to absorb the collision energy. Consequently,damage to the other parts can be avoided. Similarly, the opposed vehicleis provided with the energy absorbing pipe member and the tip member.

The present invention is carried out as described above and has thefollowing advantages.

In the collision energy absorbing structure according to the presentinvention, to deal with the collision in which the force in thelongitudinal direction of the vehicle is applied, the cutout portionwith the open cross section is formed at the front end portion of theenergy absorbing member, and from the front end portion, the deformationstarts. In other words, the substantially channel-shaped deformationstarting portion is extended from part of the front end of the energyabsorbing member. This constitution facilitates the deformation of thefront end portion and reduces the initial force peak for generating thebellows-like deformation, and also makes the deformation of the frontend portion trigger the following bellows-like deformation and reducesthe corresponding force peak. Thereby, the bellows-like deformationoccurs naturally and the collision energy can be efficiently absorbed.In other words, since the force peak in the initial stage of collisionand the following force peak can be made small and substantially equaland the constant reaction force can be maintained, the impact acting onthe passengers can be relieved without a rapid rise in the impact force.In particular, since the cutout portion is provided at the tubularenergy absorbing pipe member with rectangular cross section as theenergy absorbing member, having equal cross-section dimension and platethickness and including no inside ribs, the member can be manufacturedeasily and at a low cost.

In addition, since the plurality of impact absorbing members arevertically or laterally symmetric, the impact force in the travelingdirection can be evenly applied to the front end portion of the energyabsorbing member so as to cause the bellows-like deformation withoutfalling the energy absorbing member.

Further, since the rubber damper is connected to the vehicle coupler,for relieving the impact generated between the vehicles, the front endportion of the energy absorbing member is connected to the rear endportion of the rubber damper, and the rear end portion of the energyabsorbing member is connected to the draft stop mounted to the vehiclebody frame, the small collision energy can be absorbed by the rubberdamper and the great collision energy can be absorbed by bellows-likedeformation of the energy absorbing member.

Still further, by providing the energy absorbing member behind the railguard board for eliminating obstacles on the rail during traveling andconnecting the rear end portion of the energy absorbing member to thevehicle body frame by means of the support device, the excessivecollision energy applied to the rail guard board can be absorbed by thebellows-like deformation of the energy absorbing member.

Moreover, by connecting the rear end portion of the energy absorbingmember extending forwardly of the coupler and provided with thecollision member at the front end to the front end portion of thesupport device (support pipe member) mounted to the vehicle body frame,provided behind the coupler, and extending forwardly of the rail guardboard, the collision energy can be absorbed by the bellows-likedeformation of the energy absorbing member and the impact acting on thepassengers can be relieved.

As this invention may be embodied in several forms without departingfrom the spirit of essential characteristics thereof, the presentembodiments are therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within metersand bounds of the claims, or equivalence of such meters and boundsthereof are therefore intended to be embodied by the claims.

1. A collision energy absorbing structure of a vehicle comprising: a tubular and energy absorbing member with rectangular cross section, provided in the longitudinal direction of the vehicle and having four flat plate portions, the tubular energy absorbing member being adapted to receive a collision force in the longitudinal direction of the vehicle and deformed like bellows by buckling, so as to absorb a collision energy; a deformation starting portion provided by forming a cut out portion in one of right and left sides while one of upper and lower sides of a front end portion of the energy absorbing member; and a rubber damper connected to a coupler of the vehicle, for relieving impact generated between collided vehicles, wherein a front end portion of the energy absorbing member is connected to a rear end portion of the rubber damper and a rear end portion of the energy absorbing member is connected to a draft stop mounted to a vehicle body frame.
 2. The collision energy absorbing structure according to claim 1, wherein the energy absorbing member is provided behind a rail guard board for eliminating obstacles on a rail during traveling and a rear end portion of the energy absorbing member is connected to a support device mounted to a vehicle body frame.
 3. The collision energy absorbing structure according to claim 1, further comprising: a support device mounted to the vehicle body frame, provided behind a coupler, and extending forwardly of a rail guard board, wherein a rear end portion of the energy absorbing member is connected to a front end portion of the support device, and the energy absorbing member extends forwardly of the coupler.
 4. The collision energy absorbing structure according to claim 1, wherein a plurality of energy absorbing members are provided so as to be vertically or laterally symmetric.
 5. The collision energy absorbing structure according to claim 4, further comprising: a rubber damper connected to a coupler of the vehicle, for relieving impact generated between collided vehicles, wherein a front end portion of the energy absorbing member is connected to a rear end portion of the rubber damper and a rear end portion of the energy absorbing member is connected to a draft stop mounted to the vehicle body frame.
 6. The collision energy absorbing structure according to claim 4, wherein the energy absorbing member is provided behind a rail guard board for eliminating obstacles on a rail during traveling and the rear end portion of the energy absorbing member is connected to a support device mounted to the vehicle body frame.
 7. The collision energy absorbing structure according to claim 4, further comprising: a support device mounted to the vehicle body frame, provided behind a coupler, and extending forwardly of a rail guard board, wherein the rear end portion of the energy absorbing member is connected to a front end portion of the support device, and the energy absorbing member extends forwardly of the coupler. 